Preheat oven to 350 °F (180 °C). Butter a 10-in (25 cm) Bundt pan or two 9 x 5-in (23 x 13 cm) loaf pans.
In a bowl, gradually whisk milk into cocoa powder to make a smooth paste; whisk in yoghurt and set aside.
In another bowl, combine flour, baking powder, baking soda and salt.
In a large bowl, using an electric mixer, beat butter with sugar until light and fluffy; beat in eggs and vanilla extract.
Using a wooden spoon, stir in flour mixture alternately with milk mixture, making 3 additions of flour and 2 of milk. Fold in chocolate chips and raspberries.
Spread into prepared pan, smoothing top. Bake for 60 to 70 min or until a tester inserted in centre comes out with a few moist crumbs clinging to it. Let cool in pan on a rack for 15 min. Invert onto rack, remove pan and let cool completely.
Allow to cool. Store in an airtight container. You can also freeze half or all of it, wrap in parchment paper, then place in a zippy bag. Defrost as normal and enjoy! It will still be moist.